Modification of PP with CNT as painting agent: influence on performance of injected pieces

MARIA ALEJANDRA COSTANTINO; ANTONIO PONTES; CAREN ROSALES; JULIO VIANA; LEANDRO RAMAJO ; VALERIA PETTARIN

Conferencia; , PMI2018 International Conference on Polymers and Mould Innovations; 2018

From an industrial point of view, final plastic products should meet both certain structural re-quirements and adequate aesthetic quality. Manufactured pieces are commonly subjected to different surface finishing techniques to achieve desired aesthetic requirements, being the electrostatic painting the most effi-cient procedure. It offers great economic, environmental and cosmetic advantages, among the great reduction of used paint and volatile emissions as the most relevant. However, this technique cannot be directly applied in polymers due to their insulating properties. Plastic pieces need to be previously prepared by painting them with a primer, adding a further stage to the production cycle. To avoid this extra step, a painting agent could be added to the polymer to modify its electrical properties and make it suitable to be directly electrostatic painted. Carbon nanotubes (CNT) were proposed in this work as an electrostatic painting assistant for poly-propylene (PP) injected pieces. The present work aims to evaluate how CNTs ? added to increase the panting transfer efficiency ? influence the mechanical performance of intricate PP injected moldings. Then a complete characterization, including morphological, electrical and mechanical characterization ? and their relationship ? of double gated injection molded PP/CNT parts is presented. Differences in CNT orientation were found along the pieces: while a CNT orientation profile was observed along the thickness of the injected part in-duced by the molding thermo-mechanical field, CNT were seen randomly distributed in the weld line zone. These dissimilar orientations induce a difference of an order of magnitude in the electrical properties of the part that would result in distinct paint transfer efficiency in the same piece. Moreover, mechanical perfor-mance of pieces was degraded by the addition of only 3% of CNT, especially in the weld line zone.